The present invention relates to multiple cone-type synchronizers for manual transmissions and, more particularly, to an improved dual-cone synchronizer mechanism incorporating servo action.
In general, most synchronizer mechanisms typically used in manual transmissions and transfer cases are either of the "strut" or "strutless" types. Strutless synchronizers, such as disclosed in U.S. Pat. No. 3,700,083 issued Oct. 29, 1972 to N. Ashikawa, et al. typically employ a thrust member, such as an annular spring, interposed between a clutch sleeve and a blocker ring. The annular spring is mounted on the outer surface of a plurality of uniformly spaced lugs integrally formed on the blocker ring. Upon axial movement of the clutch sleeve the annular spring acts on the blocker ring to energize the synchronizer mechanism for generating sufficient cone torque to "clock" the blocker ring to a blocking position. Once synchronization is complete, the clutch sleeve passes over the annular spring and into lock-up engagement with a ratio gear such that torque is transmitted to the driven gear.
Strut-type synchronizers, such as disclosed in U.S. Pat. No. 4,566,568 issued Jan. 28, 1986 to Yant include a spring member radially interposed between the hub and the clutch sleeve for biasing a strut radially outwardly into engagement with a detent groove formed in the inner bore of the clutch sleeve. Axial displacement of the clutch sleeve causes the strut to act on the blocker ring for energizing the synchronizer mechanism to block further axial displacement of the clutch sleeve until speed synchronization is complete.
A primary design constraint associated with many conventional cone-type synchronizers however, is their inability to generate sufficient synchronizing torque capacity. This is due largely to dimensional limitations associated with the friction generating components utilized within the synchronizer mechanism. Typically, the "input" force applied by the vehicle operator during a gear shift is the only force exerted for generating the frictional "cone" torque required for speed synchronization.